Weaving machines and dobbies which control same are built separately, usually by different manufacturers, and are assembled onto one another according to the needs. However, both machines operate synchronously wherein the drive motor of the weaving machine acts simultaneously as a drive for the dobby. The power transmission from the weaving machine onto the dobby is accomplished by means of a continuous belt which extends over disks of the two drive shafts. Great demands with respect to exactness - because of the synchronous mode of operation - and durability during day and night continuous operation are thereby placed on this power transmission.
It is known to use for transmission a chain drive, for example a roller chain. A quieter run, at a considerable reduction in cost, is achieved, however, with the lately used toothed belt, namely an endless leather, rubber, plastic or textile belt which has toothlike strips or ribs on its inside surface. All of these drives have tension rollers to reduce vibrations in the belt or the chain and to counteract a slip danger, which tension rollers consist of a roller which is under spring or weight tension.
While in the case of chain drives the axial parallelism of the shafts and of the tension roller plays rather a subordinate role, in the case of a toothed belt drives a very high exactness must be maintained with respect to this so that the belt does not at all times tend to move axially on the guide disks and result in a premature wear. Moreover, it is not permitted in toothed belt drives, like in flat belts, to use embossed belt disks in order to prevent the belt from drifting laterally.
Great difficulties exist during attachment of the dobbies to weaving machines to maintain an exact axial parallelism of the drive shafts of the two machines. Such inexactnesses lead according to well-known principles to a lateral drifting of the belt. However, one can, within certain limits, overcome the consequences of this error by arranging the axle of the tensioning means sloped with respect to the axes of the belt disks. The sloped position is thereby empirically optimized. Constructions have already been developed which permit an adjustment of the bearing axle of the tension roller in any desired direction. This empirical adjustment, however, demands a lot of experience and a great adjustment work input, this in particular because the known constructions facilitate an adjustment of the tension roller only during standstill. To determine the best position in which the toothed belts have the smallest tendency for axial drifting, the machine must be observed during operation and must be switched off for correction.
The object of the invention is to increase the security of the power-transmitting mechanism and a simplification and reduction in price of the adjustment operations.
This is achieved with a tension roller which is characterized inventively by the axle of the roller being spherically adjustably supported on a pivotal lever and having means for facilitating its adjustment and locking it in place.
The tension roller can with this be adjusted finely and can be locked during the operation of the machines in more than one plane.